* [PATCH v3] sched/deadline: remove useless param from setup_new_dl_entity
@ 2016-07-08 11:28 Juri Lelli
2016-07-11 5:03 ` Xunlei Pang
0 siblings, 1 reply; 6+ messages in thread
From: Juri Lelli @ 2016-07-08 11:28 UTC (permalink / raw)
To: peterz; +Cc: rostedt, linux-kernel, mingo, luca.abeni, juri.lelli
setup_new_dl_entity() takes two parameters, but it only actually uses
one of them, under a different name, to setup a new dl_entity, after:
2f9f3fdc928 "sched/deadline: Remove dl_new from struct sched_dl_entity"
as we currently do
setup_new_dl_entity(&p->dl, &p->dl)
However, before Luca's change we were doing
setup_new_dl_entity(dl_se, pi_se)
in update_dl_entity() for a dl_se->new entity: we were using pi_se's
parameters (the potential PI donor) for setting up a new entity.
Restore this behaviour (as we want to correctly initialize parameters of
a boosted task that enters DEADLINE) by removing the useless second
parameter of setup_new_dl_entity() and retrieving the top waiter
directly from inside that function.
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Luca Abeni <luca.abeni@unitn.it>
Signed-off-by: Juri Lelli <juri.lelli@arm.com>
---
Changes from v2:
- optimize by calling rt_mutex_get_top_task only if the task is
boosted (as suggested by Steve)
Changes from v1:
- Steve pointed out that we were actually using the second parameter
to permorm initialization
- Luca confirmed that behavior is slightly changed w.r.t. before his
change
- changelog updated and original behavior restored
---
kernel/sched/deadline.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index fcb7f0217ff4..7aeb21963d3c 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -346,11 +346,12 @@ static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
* one, and to (try to!) reconcile itself with its own scheduling
* parameters.
*/
-static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se,
- struct sched_dl_entity *pi_se)
+static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
{
struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
struct rq *rq = rq_of_dl_rq(dl_rq);
+ struct task_struct *pi_task;
+ struct sched_dl_entity *pi_se = dl_se;
WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
@@ -363,6 +364,15 @@ static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se,
return;
/*
+ * Use the scheduling parameters of the top pi-waiter task,
+ * if we have one from which we can inherit a deadline.
+ */
+ if (dl_se->dl_boosted &&
+ (pi_task = rt_mutex_get_top_task(dl_task_of(dl_se))) &&
+ dl_prio(pi_task->normal_prio))
+ pi_se = &pi_task->dl;
+
+ /*
* We use the regular wall clock time to set deadlines in the
* future; in fact, we must consider execution overheads (time
* spent on hardirq context, etc.).
@@ -1721,7 +1731,7 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
static void switched_to_dl(struct rq *rq, struct task_struct *p)
{
if (dl_time_before(p->dl.deadline, rq_clock(rq)))
- setup_new_dl_entity(&p->dl, &p->dl);
+ setup_new_dl_entity(&p->dl);
if (task_on_rq_queued(p) && rq->curr != p) {
#ifdef CONFIG_SMP
--
2.7.4
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v3] sched/deadline: remove useless param from setup_new_dl_entity
2016-07-08 11:28 [PATCH v3] sched/deadline: remove useless param from setup_new_dl_entity Juri Lelli
@ 2016-07-11 5:03 ` Xunlei Pang
2016-07-11 8:01 ` luca abeni
0 siblings, 1 reply; 6+ messages in thread
From: Xunlei Pang @ 2016-07-11 5:03 UTC (permalink / raw)
To: Juri Lelli, peterz; +Cc: rostedt, linux-kernel, mingo, luca.abeni
On 2016/07/08 at 19:28, Juri Lelli wrote:
> setup_new_dl_entity() takes two parameters, but it only actually uses
> one of them, under a different name, to setup a new dl_entity, after:
>
> 2f9f3fdc928 "sched/deadline: Remove dl_new from struct sched_dl_entity"
>
> as we currently do
>
> setup_new_dl_entity(&p->dl, &p->dl)
>
> However, before Luca's change we were doing
>
> setup_new_dl_entity(dl_se, pi_se)
>
> in update_dl_entity() for a dl_se->new entity: we were using pi_se's
> parameters (the potential PI donor) for setting up a new entity.
>
> Restore this behaviour (as we want to correctly initialize parameters of
> a boosted task that enters DEADLINE) by removing the useless second
> parameter of setup_new_dl_entity() and retrieving the top waiter
> directly from inside that function.
>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Luca Abeni <luca.abeni@unitn.it>
> Signed-off-by: Juri Lelli <juri.lelli@arm.com>
>
> ---
> Changes from v2:
> - optimize by calling rt_mutex_get_top_task only if the task is
> boosted (as suggested by Steve)
>
> Changes from v1:
> - Steve pointed out that we were actually using the second parameter
> to permorm initialization
> - Luca confirmed that behavior is slightly changed w.r.t. before his
> change
> - changelog updated and original behavior restored
> ---
> kernel/sched/deadline.c | 16 +++++++++++++---
> 1 file changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index fcb7f0217ff4..7aeb21963d3c 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -346,11 +346,12 @@ static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
> * one, and to (try to!) reconcile itself with its own scheduling
> * parameters.
> */
> -static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se,
> - struct sched_dl_entity *pi_se)
> +static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
> {
> struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
> struct rq *rq = rq_of_dl_rq(dl_rq);
> + struct task_struct *pi_task;
> + struct sched_dl_entity *pi_se = dl_se;
>
> WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
>
> @@ -363,6 +364,15 @@ static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se,
> return;
>
> /*
> + * Use the scheduling parameters of the top pi-waiter task,
> + * if we have one from which we can inherit a deadline.
> + */
> + if (dl_se->dl_boosted &&
> + (pi_task = rt_mutex_get_top_task(dl_task_of(dl_se))) &&
> + dl_prio(pi_task->normal_prio))
> + pi_se = &pi_task->dl;
> +
> + /*
> * We use the regular wall clock time to set deadlines in the
> * future; in fact, we must consider execution overheads (time
> * spent on hardirq context, etc.).
> @@ -1721,7 +1731,7 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
> static void switched_to_dl(struct rq *rq, struct task_struct *p)
> {
> if (dl_time_before(p->dl.deadline, rq_clock(rq)))
> - setup_new_dl_entity(&p->dl, &p->dl);
> + setup_new_dl_entity(&p->dl);
I'm curious why we even call setup_new_dl_entity() for non-queued cases?
It seems more reasonable to do it when it really gets queued. We can see
that enqueue_task_dl()->update_dl_entity() also has the same update logic
as switched_to_dl().
If so, for already queued and boosted cases, rt_mutex_setprio() will call
enqueue_task() with ENQUEUE_REPLENISH set, so enqueue_dl_entity()
->replenish_dl_entity() will advance p->dl.deadline beforehand, see code:
replenish_dl_entity():
if (dl_se->dl_deadline == 0) {
dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
dl_se->runtime = pi_se->dl_runtime;
}
IOW, we don't need to handle !dl boosted cases in setup_new_dl_entity().
Regards,
Xunlei
>
> if (task_on_rq_queued(p) && rq->curr != p) {
> #ifdef CONFIG_SMP
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v3] sched/deadline: remove useless param from setup_new_dl_entity
2016-07-11 5:03 ` Xunlei Pang
@ 2016-07-11 8:01 ` luca abeni
2016-07-11 8:16 ` Xunlei Pang
0 siblings, 1 reply; 6+ messages in thread
From: luca abeni @ 2016-07-11 8:01 UTC (permalink / raw)
To: Xunlei Pang; +Cc: Juri Lelli, peterz, rostedt, linux-kernel, mingo
Hello,
On Mon, 11 Jul 2016 13:03:56 +0800
Xunlei Pang <xpang@redhat.com> wrote:
> On 2016/07/08 at 19:28, Juri Lelli wrote:
[...]
> > @@ -363,6 +364,15 @@ static inline void setup_new_dl_entity(struct
> > sched_dl_entity *dl_se, return;
> >
> > /*
> > + * Use the scheduling parameters of the top pi-waiter task,
> > + * if we have one from which we can inherit a deadline.
> > + */
> > + if (dl_se->dl_boosted &&
> > + (pi_task = rt_mutex_get_top_task(dl_task_of(dl_se))) &&
> > + dl_prio(pi_task->normal_prio))
> > + pi_se = &pi_task->dl;
> > +
> > + /*
> > * We use the regular wall clock time to set deadlines in
> > the
> > * future; in fact, we must consider execution overheads
> > (time
> > * spent on hardirq context, etc.).
> > @@ -1721,7 +1731,7 @@ static void switched_from_dl(struct rq *rq,
> > struct task_struct *p) static void switched_to_dl(struct rq *rq,
> > struct task_struct *p) {
> > if (dl_time_before(p->dl.deadline, rq_clock(rq)))
> > - setup_new_dl_entity(&p->dl, &p->dl);
> > + setup_new_dl_entity(&p->dl);
>
> I'm curious why we even call setup_new_dl_entity() for non-queued
> cases? It seems more reasonable to do it when it really gets queued.
> We can see that enqueue_task_dl()->update_dl_entity() also has the
> same update logic as switched_to_dl().
I wondered the same when removing the dl_new field from
sched_dl_entity... But then I realised that enqueue_dl_entity() does
not always invoke update_dl_entity() or replenish_dl_entity()... For
example, when a task switches from SCHED_OTHER (or RT) to -deadline due
to sched_setattr() (or similar) these functions are not invoked.
Luca
> If so, for already queued and boosted cases, rt_mutex_setprio() will
> call enqueue_task() with ENQUEUE_REPLENISH set, so enqueue_dl_entity()
> ->replenish_dl_entity() will advance p->dl.deadline beforehand, see
> code: replenish_dl_entity():
> if (dl_se->dl_deadline == 0) {
> dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
> dl_se->runtime = pi_se->dl_runtime;
> }
>
> IOW, we don't need to handle !dl boosted cases in
> setup_new_dl_entity().
>
> Regards,
> Xunlei
>
> >
> > if (task_on_rq_queued(p) && rq->curr != p) {
> > #ifdef CONFIG_SMP
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v3] sched/deadline: remove useless param from setup_new_dl_entity
2016-07-11 8:01 ` luca abeni
@ 2016-07-11 8:16 ` Xunlei Pang
2016-07-11 9:22 ` luca abeni
2016-07-12 8:42 ` Juri Lelli
0 siblings, 2 replies; 6+ messages in thread
From: Xunlei Pang @ 2016-07-11 8:16 UTC (permalink / raw)
To: luca abeni; +Cc: Juri Lelli, peterz, rostedt, linux-kernel, mingo
On 2016/07/11 at 16:01, luca abeni wrote:
> Hello,
>
> On Mon, 11 Jul 2016 13:03:56 +0800
> Xunlei Pang <xpang@redhat.com> wrote:
>
>> On 2016/07/08 at 19:28, Juri Lelli wrote:
> [...]
>>> @@ -363,6 +364,15 @@ static inline void setup_new_dl_entity(struct
>>> sched_dl_entity *dl_se, return;
>>>
>>> /*
>>> + * Use the scheduling parameters of the top pi-waiter task,
>>> + * if we have one from which we can inherit a deadline.
>>> + */
>>> + if (dl_se->dl_boosted &&
>>> + (pi_task = rt_mutex_get_top_task(dl_task_of(dl_se))) &&
>>> + dl_prio(pi_task->normal_prio))
>>> + pi_se = &pi_task->dl;
>>> +
>>> + /*
>>> * We use the regular wall clock time to set deadlines in
>>> the
>>> * future; in fact, we must consider execution overheads
>>> (time
>>> * spent on hardirq context, etc.).
>>> @@ -1721,7 +1731,7 @@ static void switched_from_dl(struct rq *rq,
>>> struct task_struct *p) static void switched_to_dl(struct rq *rq,
>>> struct task_struct *p) {
>>> if (dl_time_before(p->dl.deadline, rq_clock(rq)))
>>> - setup_new_dl_entity(&p->dl, &p->dl);
>>> + setup_new_dl_entity(&p->dl);
>> I'm curious why we even call setup_new_dl_entity() for non-queued
>> cases? It seems more reasonable to do it when it really gets queued.
>> We can see that enqueue_task_dl()->update_dl_entity() also has the
>> same update logic as switched_to_dl().
> I wondered the same when removing the dl_new field from
> sched_dl_entity... But then I realised that enqueue_dl_entity() does
> not always invoke update_dl_entity() or replenish_dl_entity()... For
> example, when a task switches from SCHED_OTHER (or RT) to -deadline due
> to sched_setattr() (or similar) these functions are not invoked.
Yeah, but for wake-up cases it does, as ENQUEUE_WAKEUP is set.
What I meant is, can we only update for queued tasks in switched_to_dl()?
Regards,
Xunlei
>
>
> Luca
>
>> If so, for already queued and boosted cases, rt_mutex_setprio() will
>> call enqueue_task() with ENQUEUE_REPLENISH set, so enqueue_dl_entity()
>> ->replenish_dl_entity() will advance p->dl.deadline beforehand, see
>> code: replenish_dl_entity():
>> if (dl_se->dl_deadline == 0) {
>> dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
>> dl_se->runtime = pi_se->dl_runtime;
>> }
>>
>> IOW, we don't need to handle !dl boosted cases in
>> setup_new_dl_entity().
>>
>> Regards,
>> Xunlei
>>
>>>
>>> if (task_on_rq_queued(p) && rq->curr != p) {
>>> #ifdef CONFIG_SMP
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v3] sched/deadline: remove useless param from setup_new_dl_entity
2016-07-11 8:16 ` Xunlei Pang
@ 2016-07-11 9:22 ` luca abeni
2016-07-12 8:42 ` Juri Lelli
1 sibling, 0 replies; 6+ messages in thread
From: luca abeni @ 2016-07-11 9:22 UTC (permalink / raw)
To: Xunlei Pang; +Cc: Juri Lelli, peterz, rostedt, linux-kernel, mingo
On Mon, 11 Jul 2016 16:16:20 +0800
Xunlei Pang <xpang@redhat.com> wrote:
> On 2016/07/11 at 16:01, luca abeni wrote:
> > Hello,
> >
> > On Mon, 11 Jul 2016 13:03:56 +0800
> > Xunlei Pang <xpang@redhat.com> wrote:
> >
> >> On 2016/07/08 at 19:28, Juri Lelli wrote:
> > [...]
> >>> @@ -363,6 +364,15 @@ static inline void setup_new_dl_entity(struct
> >>> sched_dl_entity *dl_se, return;
> >>>
> >>> /*
> >>> + * Use the scheduling parameters of the top pi-waiter
> >>> task,
> >>> + * if we have one from which we can inherit a deadline.
> >>> + */
> >>> + if (dl_se->dl_boosted &&
> >>> + (pi_task = rt_mutex_get_top_task(dl_task_of(dl_se)))
> >>> &&
> >>> + dl_prio(pi_task->normal_prio))
> >>> + pi_se = &pi_task->dl;
> >>> +
> >>> + /*
> >>> * We use the regular wall clock time to set deadlines in
> >>> the
> >>> * future; in fact, we must consider execution overheads
> >>> (time
> >>> * spent on hardirq context, etc.).
> >>> @@ -1721,7 +1731,7 @@ static void switched_from_dl(struct rq *rq,
> >>> struct task_struct *p) static void switched_to_dl(struct rq *rq,
> >>> struct task_struct *p) {
> >>> if (dl_time_before(p->dl.deadline, rq_clock(rq)))
> >>> - setup_new_dl_entity(&p->dl, &p->dl);
> >>> + setup_new_dl_entity(&p->dl);
> >> I'm curious why we even call setup_new_dl_entity() for non-queued
> >> cases? It seems more reasonable to do it when it really gets
> >> queued. We can see that enqueue_task_dl()->update_dl_entity() also
> >> has the same update logic as switched_to_dl().
> > I wondered the same when removing the dl_new field from
> > sched_dl_entity... But then I realised that enqueue_dl_entity() does
> > not always invoke update_dl_entity() or replenish_dl_entity()... For
> > example, when a task switches from SCHED_OTHER (or RT) to -deadline
> > due to sched_setattr() (or similar) these functions are not
> > invoked.
>
> Yeah, but for wake-up cases it does, as ENQUEUE_WAKEUP is set.
> What I meant is, can we only update for queued tasks in
> switched_to_dl()?
Uhm... Looking at this code again, I am not sure anymore about it...
(switched_to_dl() is invoked after enqueue enqueue_task_dl()?)
Maybe the best thing to do is to move the
"if (dl_time_before(p->dl.deadline, rq_clock(rq)))"
check in enqueue_dl_entity() (Juri, what do you think)? I'll try this
approach in the next days.
Thanks,
Luca
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v3] sched/deadline: remove useless param from setup_new_dl_entity
2016-07-11 8:16 ` Xunlei Pang
2016-07-11 9:22 ` luca abeni
@ 2016-07-12 8:42 ` Juri Lelli
1 sibling, 0 replies; 6+ messages in thread
From: Juri Lelli @ 2016-07-12 8:42 UTC (permalink / raw)
To: xlpang; +Cc: luca abeni, peterz, rostedt, linux-kernel, mingo
On 11/07/16 16:16, Xunlei Pang wrote:
> On 2016/07/11 at 16:01, luca abeni wrote:
> > Hello,
> >
> > On Mon, 11 Jul 2016 13:03:56 +0800
> > Xunlei Pang <xpang@redhat.com> wrote:
> >
> >> On 2016/07/08 at 19:28, Juri Lelli wrote:
> > [...]
> >>> @@ -363,6 +364,15 @@ static inline void setup_new_dl_entity(struct
> >>> sched_dl_entity *dl_se, return;
> >>>
> >>> /*
> >>> + * Use the scheduling parameters of the top pi-waiter task,
> >>> + * if we have one from which we can inherit a deadline.
> >>> + */
> >>> + if (dl_se->dl_boosted &&
> >>> + (pi_task = rt_mutex_get_top_task(dl_task_of(dl_se))) &&
> >>> + dl_prio(pi_task->normal_prio))
> >>> + pi_se = &pi_task->dl;
> >>> +
> >>> + /*
> >>> * We use the regular wall clock time to set deadlines in
> >>> the
> >>> * future; in fact, we must consider execution overheads
> >>> (time
> >>> * spent on hardirq context, etc.).
> >>> @@ -1721,7 +1731,7 @@ static void switched_from_dl(struct rq *rq,
> >>> struct task_struct *p) static void switched_to_dl(struct rq *rq,
> >>> struct task_struct *p) {
> >>> if (dl_time_before(p->dl.deadline, rq_clock(rq)))
> >>> - setup_new_dl_entity(&p->dl, &p->dl);
> >>> + setup_new_dl_entity(&p->dl);
> >> I'm curious why we even call setup_new_dl_entity() for non-queued
> >> cases? It seems more reasonable to do it when it really gets queued.
> >> We can see that enqueue_task_dl()->update_dl_entity() also has the
> >> same update logic as switched_to_dl().
> > I wondered the same when removing the dl_new field from
> > sched_dl_entity... But then I realised that enqueue_dl_entity() does
> > not always invoke update_dl_entity() or replenish_dl_entity()... For
> > example, when a task switches from SCHED_OTHER (or RT) to -deadline due
> > to sched_setattr() (or similar) these functions are not invoked.
>
> Yeah, but for wake-up cases it does, as ENQUEUE_WAKEUP is set.
> What I meant is, can we only update for queued tasks in switched_to_dl()?
>
Looks sensible to do. I think we can use the already present
task_on_rq_queued() check in there. I'll put together a v4 ASAP (if Luca
doesn't have already something).
Thanks,
- Juri
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2016-07-12 8:42 UTC | newest]
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2016-07-08 11:28 [PATCH v3] sched/deadline: remove useless param from setup_new_dl_entity Juri Lelli
2016-07-11 5:03 ` Xunlei Pang
2016-07-11 8:01 ` luca abeni
2016-07-11 8:16 ` Xunlei Pang
2016-07-11 9:22 ` luca abeni
2016-07-12 8:42 ` Juri Lelli
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